Method of making tubular bodies



Jan. 14, 1941. A. MAGNANI 2,

' v METHOD OF MAKING TUBULAR BODIES Filed Aug; 24, 1937 /3 l 1 /3 :75:11: I /2 "/5 30 90 g I I 4 1 L 1 L- v INVENT R- ATTORNEY;

Patented-Jan. 14, 1941 I UNITED STATES un'rnon ormxmc "roams. nonmsAlessandro Magnani, Broni, Italy, assignor to 1-. L. Smidth & o. AIS,Wnhagen, Denmark, a corporation of Denmark Application August 24, 1937,Serial No. 160,596 In Great Britain and Sweden March 3, 1937 1 Claim.(01. 92-543 form is distributed on the surface of a rotating molding,roller having a permeable surface, through which the water is drawn offby suction.

15 As the layer of pulp'builds up on the roller, it

is shaped by a shaping roller which rotates tangentially to the moldingroller and is pressed light y against the surface of the layer.

The patented process and apparatus are simple 20 and generallysatisfactory, but occasionally, the drawing off by suction of the waterfrom the layer of pulp on the surface of the molding roller results inthe formation of holes through the layer.

This permits air to'leak into the interior of themolding roller so thatthe suction effect is reduced and the layer is not suillciently deprivedof water. In addition, the thickness and surface of the layer are notuniform.

According to the present invention, the pulp 30 in fluent form isapplied to the water-permeable surface of a molding roller to theinterior of which suction is applied, and as the pulp builds up on theroller to produce a layer, the pulp is pressed and compacted by acalendering roller driven at 36 a higher surface speed than that of thelayer. By the use of the calendering roller, the formation of holesthrough the fibrous layer is prevented, since, if such holes initiallydevelop,- they are promptly closed by the troweling action of the t0,calendering roller. Moreover, the pressing and smoothing action of thecalendering roller tends to close the pores in the surface of thefibrous layer so that the tube so produced has an impermeable, compact,and uniform wall. For some 45 purposes, the calenderlng may be performedin succesive stages with the calendering roller operating on thefibl'OllS layer at relatively light pressure in the preliminaryoperation, and pressed more firmb against the layer in the finaloperation. Also, in some cases, it may be desirable to treat the surfaceof the tube with a reagent which causes the precipitation of solidmaterial in the surface pores of the tube, as, for example, in the caseof tubes made of asbestos cement, ll treatment of the surface thereofwith soapy prevented by glands ll.

water produces a precipitation of lime soap which fills the fine surfacepores and thus increases the impermeability of the surface.

For a better understanding of the invention, reference may be had to theaccompanying draw- 5 ing, in which Figure 1 is aplan view, with partsremoved, of apparatus which may be usedin the practice of the method ofthe invention; and

Figure 2 is an end view of the apparatus.

The apparatus as illustrated in th'e-drawing includes a molding roller10, the exterior shape of which is that of the tu'be'to be produced, theroller illustrated having an" enlargement H at one end correspondingto-the socket of the finished pipe. The roller is closed at its ends andit is mounted on a shaft l2 supported for rotation in bearings 13 onsuitable supports It. The shaft I2 is enlarged at one end, as indicatedat l5, and through the enlargement, extends a pipe I6 connected to avacuum pump, not shown, by which suction can be applied to the interiorof the roller, the leakage of air around the pipe being The roller ispreferably a seamless tube formed with a multiplicity of 2 perforationsthrough its wall and is covered by a filter cloth l8 of linen 'or thelike.

Adjacent the molding roller is a calendering roller [9 mounted on theshaft 20 which is supported in bearings 2| movably mounted on the 80support It. Means, illustrated as links 22, connected to the bearings 2|are provided for maintaining. the calendering roller l9 in tangentialcontact with the surface of the molding roller at a suitable pressure,and the shaft 20 is connected through a universal'ioint 23 to a'driveshaft 2-5, which is operated at a speed such that the surface speed ofthe calendering roller is substantially greater than that of the moldingroller.

' This may be accomplished, for instance, by driv- 4o ing the shaft 24of the calendering roller by an electric motor 29, and driving the-shafti2 of the molding roller by an independent motor 30, the two motorsbeing so controlled that the motor 29operates at the proper speed inrelation to the speed of the motor 30 to produce the desireddifferential surface speed of the two rollers. The calendering rollermay have a smooth surface, but is preferably formed with a series ofsmall circum- :fer ential grooves, which may, for example, be 1 so avalve 28 by which the rate of flow from the rate from the hopper'throughthe discharge pipe into a bi e oi'the rollers, and suction is applied tothe interior of the molding roller. A thin layeroipulpisthusappliedtothemoldingrollerand' dewatered by the withdrawal ofwater into the interior of the latter, the water beingdischarged throughthe pipe ll. As the operation proceeds, the hopper is moved back andforth along the rails 2| so as to build up a nbrous'tubmar body on themolding roller, and as the thickness'oi.

the fibrous layer increases, the calendering roller is progressivelywithdrawn from the molding roller untilalayerolthe desired thickneeshasbeen produced. The ieed otpulp is then stopped, thepressureoithecalenderingrollerlmnstthe layeriaincreased, therotationoitherolleraccntinuing until the thickness of the fibrous layerl0 permeability oi which can he further increased by the use of theprecipitating agent, as described.

I claim:

A methodoi' producing a tubular body from iibrous pulp, which comprisesdistributing the'puip 18 in slurry form on the surface or a rotating permeable tubular body to progressively build up' a layer of the pulp onsaid body, applying suction within said body to withdraw water from theslurry through the wall of said body while said to layer is beingprogresively built upon the body. and, throughout the building up of thelayer of pulp on said body.. 0ntinuously troweling the surface or thelayer simultaneously with the withdrawal of the water from the layer toconsolidate 25 the layer and clone the pom formed therein by thewithdrawal of the water.- said troweling being eil'ected by subjectingthe surface of the layer to the rubbing and smoothing action of anothersurhoepreecedagainstthesiuiaceoi thelayer and positively moved in thesame direction at a substantially higher speed.

almaammo MAGNANI.

